Sony has announced that its Reader Digital Book will be the first eBook reader to support the .epub format, the International Digital Publishing Forum’s XML-based standard format for publishing ebooks. Some of the biggest publishers in the business offer books in .epub format, including Penguin and HarperMedia.

Previously, Sony’s eReader was locked to the Sony store similar to the way the Kindle is locked to Amazon’s store and could only read books from the Sony store, .pdf and DRM-free text. Prior to this upgrade, Sony was the cheaper hardware option (about $60 less than the Kindle), but a lot of people were prepared to fork out for the extra few bucks for the Kindle in return for the more extensive library ; the Amazon store boasts over 140,000 titles while the Sony store only had a catalogue of about 45,000.

The reader will continue to support the BBeB format native to Sony’s eBook store and additionally, will support Adobe Digital Editions software enabling users to read copyright-protected PDF files.

To celebrate the decision to open up its library, Sony announced that it would be selling a limited edition version of the Reader Digital Book in red. The next version of the eReader (the PRS-505) will support the new formats straight out of the box and existing owners can download the update as of today.